Method of making toroidal coils



July 13 1926. 1,592,352

C. A. FRIEDRICH METHOD OF MAKING TOROIDAL SOILS Filed Sept. 4, 1925 v @Jw Patented July 1, 192,

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GHARLES A. FRIEDRICH, 0F BELLEROSE, NEW YORK.

METHODOF MAKING .TOROIDAL COILQ.

Application filed September 4, 1925. Serial No. 54,402.

Thisinvention relates to electric toroidal coils and has for its main object to provide a method of making such coils.

Another object is to use my new method in the practical application thereof as an inductance unit or transformer.

lt is well-known that toroidal coils are advantageous for radio transmission, because the magnetic field being substantially confined to the space between the windings, is little susceptible of picking up stray frequencies, such as are caused by the closing of switches in elevator apartments, etc. and which, with ordinary coils, are generally picked up by the greater magnetic field around the coils.

The construction of toroidal coils is greatly simplified and cheapened by my new method. The latter consists in that the coil is first wound as usual around a cylindrical longitudinally split mandrel and after it is completed and before it is removed from the mandrel, a comparatively thin layer or strip of a chemical compound, such as cellulose compound dissolved in ether, is applied to extend throughout the entire length of and in a straight line on one side of the circumference of the coil. The chemical compound has the capacity of shrinking considerably while drying, as a result of which, when the tubular or cylindrical coil is removed from the mandrel, it will cause the coil to curve intothe shape known as toroidal.

In the practical application of this coil as an inductance unit or transformer, the coil is enclosed in a substantially fiat casing of dielectric material so shaped as to form an annular seat or socket to hold the toroidal coil,

My invention will be fully understood by reference to the accompan ing drawing in which similar reference c aracters denote corresponding parts and in which Figs. 1 and 2 illustrate the method of making the toroidal coil; Fig. 3 shows a completed toroidal coil made according to my new method and Figs. a and 5 show an elevation and section on line 5-5 of Fig. l respectively of a complete inductance unit embodying my new coil.

Referring first to Figs. 1, 2 and 3, 10 denotes a cylindrical hollow mandrel, which is split longitudinally as at 10 and also partly circumferentially as at 10 in order to render said mandrel somewhat resilient.

Prior to winding the coil, a cylindrical core 11 of wood or the like is inserted into the mandrel, whereby the latter is stiffened. The wire 12 is then wound tightly around the mandrel in the usual manner with the windings close to one another. When the coil is completed, alayer 13 of a certain chemical compound, such as ether cellulose compound, is apphed to one side of the circumference of the coil to extend in a straight line throughout thelen th of the coil and the latter is then remove from the mandrel, after first removing the core. The chemical compound has the capacity to shrink con siderably while drying, as a result of which the coil will assume the toroidal shape 12 shown in Fig. 3.

When usin it as an inductance unit or transformer, t e two toroidal coils (primary and secondary) are placed endwise completing the circle or mug and are both en closed in a casing having an annular seator socket in which the coils are held in proper relative position.

In Figs. 4 and 5, 14 denotes a sectional disc-shaped casing of dielectric material, each section being provided with an annular cavity, which, when the sections are assembled, together form a seat or socket ll 1i to hold the two coils in position.

The smaller primary coil 12, which is made by the same method, is placed between the ends of the secondary coil 12, so that the two complete a circle. The central parts 15 of the two sections are centrally perforated as at 15 for the passage of a pin (not shown) serving for the attachment of the unit to the panel of a radio set or the like. The ends of the two coils are connected to metal eyelets 16 extending between the said central parts 15 of the sections of the cas ing and whose ends are fixed to and project outwardly from the casing to form terminals, as indicated in Fig. 4.

What I claim is 1. A method of making a toroidal electric coil, consisting in first winding a cylindrical coil and then applying to one side of the circumference of said coil a layer of shrinkage causing substance which will cause said coil to adopt and be maintained in the shape of a tore.

2. A method of making a toroidal electric coil, consisting in first windin the wire around a cylindrical mandrel, t on applying to one side of the circumference of thewindings a layer of shrinkage causing s'nlastance, then removing said cylindrical coil from the mandrel and drying said substance said substance while drying causing saidl coil to ado t the shape of s tors.

3. A met 0d ofmalring a toroidal electric coil, consisting in first Winding n cylindrical coil and then applying means to one side of its circumference to automatically cause onaco said cylindrical coil to assume a toroidal shape,

l. A toroidal coil mode by Winding on the mandrel in comlainsition with means which automatically causes 'lzlio coil to assume the Shape of a tors,

"in lcslimony Wlicrcol l n fix my signature.

@HARELES A. FRIEDRICH. 

